In the balancing of rotating bodies, the unbalance is first determined during a test run, and thereafter usually in a further separate apparatus, a corresponding material removal by milling or boring is carried out at the determined compensation locations or corresponding compensation weights are secured in the prescribed compensation planes.
In the balancing of vehicle wheels, however, the determined unbalances are compensated only by the securing of compensation weights on the wheel rims or disk wheels, because a material removal there is excluded. For this, on steel wheel rims, the compensation weights are still mostly clamped tight on the inwardly-lying and outwardly-lying wheel rim flange of the corresponding compensation locations, for which pre-fabricated weights are provided in stepped weight sizes. Due to the multiplicity of the weight steps and the exact application of the weight clamps, such a balancing is still carried out largely manually even in the industrial production of new vehicle wheels.
At the present time, for weight reasons and due to the optical configuration, frequently vehicle wheels with light metal rims are preferably utilized for new vehicles, whereby the compensation weights are usually glued-on in the wheel rim bowl in two compensation planes that are axially spaced apart from one another. For that, partially automated balancing methods are known, which have considerably accelerated the balancing process.
A method and an apparatus for applying unbalance compensation weights onto a vehicle wheel with a program-controlled handling device in the form of a robot is already known from the DE 199 61 828 B4. Therein, a vehicle wheel that is to be balanced and that is transported in by a feed or supply line is grasped by an industrial robot and rotated about its wheel axis into a compensation position, and thereby is delivered to a first weight application tool for the first compensation plane. Before that, adhesive weight elements in the determined weight class were apparently manually provided to this weight application tool, previously the protective film was pulled off, and then the first compensation weight was applied by the first weight application tool in the provided first compensation plane. Thereafter, the robot again grasps the wheel and transports it to a second weight application tool for the second compensation plane, whereby in a similar manner the second compensation weight is glued or beaten onto the determined compensation surface. This partially automated method is primarily utilized in order to be able to apply both vehicle wheels with adhesive weights as well as vehicle wheels with beat-on weights, in one balancing line without equipment change-over work. Thereby, with this method, only the supplying and the rotating of the wheels into the determined angular position is automated, so that the cycle or station time decisively depends on the speed with which the determined individual weight steps can be selected and provided to the weight application tool and thereafter applied.
From the DE 100 06 176 A1, however, there is previously known exclusively an apparatus for the securing of compensation weights with an adhesive layer, in which the gluing or adhesive mounting is carried out largely automatically though. For that a guide arrangement is provided, which includes an angled arm that reaches into the disk wheel or wheel rim bowl, and on the forward end of which a press-on element is secured. For the balancing, first an adhesive weight with a correspondingly stepped weight value is manually set into a holding arrangement of the press-on element and the protective film is removed from the adhesive layer. Then the automated gluing or adhesive-bonding process is carried out, in which the arm submerges or extends linearly so far into the wheel rim bowl until it has reached the provided compensation plane. Then the wheel is positioned into the determined angular position, and through a radial arm movement then the press-on element is pressed onto the compensation location with a prescribed force. Thereby the adhesive weight contacts with its adhesive surface onto the compensation surface in the wheel rim bowl and is secured there by the adhesive bond. By the special embodiment or construction of the press-on element with leaf spring elements, the compensation weight is first applied in the middle of the compensation surface and by increasing the press-on force and deformation of the leaf spring elements it is also uniformly pressed onto the concavely curved press-on surface in the wheel rim bowl.
For the compensation of the vehicle wheel in the second compensation plane, the arm must again be moved linearly out of the wheel rim bowl and again manually be equipped or supplied with a provided compensation weight, whereby the previously described process is then again repeated, in order to completely balance a vehicle wheel. Due to the given facts of the construction of the disk wheel or the wheel rim, it can also be necessary to provide several weights in one compensation plane, whereby the compensation time increases considerably. In a currently typical cycle time or station time of one minute in the automobile industry, even such a partially automated balancing of five vehicle wheels per production unit in one minute is not possible with such a balancing machine. This prescribed cycle time or station time can then only be achieved with several parallel-arranged balancing machines or by a remotely located separate balancing of the wheels, for which then however the respectively needed wheel sets must be stocked and supplied in the exact cycle time.
A balancing apparatus for vehicle wheels with a short cycle time is, however, already known from the DE 199 22 085 A1. For that, preferably a program-controlled bent arm robot is provided, of which the pivot arm automatically moves to the compensation surface within the wheel rim bowl and uniformly presses-on the compensation weights radially onto the concave cylindrical compensation surfaces with a press-on arrangement. In that regard, the press-on arrangement consists of a special holding arrangement with two clamp jaws on which the provided compensation weight is clamped-in between two holding jaws. By the two clamping jaws, the compensation weight is uniformly pressed-on to the concavely curved compensation surfaces within the wheel rim bowl, and is secured or held by the adhesive surface that was previously removed from the protective film.
For the completely automatic balancing, the previously determined compensation weight is apparently unrolled from a roll in a separate preparation arrangement, and is cut-off to the corresponding length and released from the protective film. This compensation weight is then given over to the robot arm or its press-on arrangement, whereby it must be exactly clamped into the holding arrangements, which requires a very exact coordination of the two motion sequences. Especially in connection with rapid cycle times or station times and the thereby necessitated accelerations of the two transfer arms, transfer errors or faults are not excluded and can lead to longer production interruptions.